Magnetic separator

ABSTRACT

A magnet assembly for use such as in a magnetic separator having means for providing increased lines of flux, increased effective pole area, decreased gap length, improved repelling of flux leak lines at the edges of the magnet poles and reduction in the flux leakage at the rear face of the magnet. Herein these means comprise a magnet element disposed at the extremities of the respective poles to define aiding poles in the magnetic circuit.

United States Patent Morgan [451 July 18, 1972 [541 MAGNETIC SEPARATOR 2,992,737 7/1961 suus 209/223 R 2,992,733 7/1961 Buus etal. u209/219 [72] Inventor' um G' Mmm Mlwaukee' WS' 3,489,280 1/1970 lsraelson et al. .209/223 R [73] Assignee: Electronic Memories & Mggnetics Car- 3,387,707 6/ 1968 Smith 335/206 poration, Los Angeles, Calif. Ex H ld B Primary amneraro roome [22] Flled: June lo 1970 Attorney-Hofgren, Wegner, Allen, Stellman & McCord 2l A l. No.: 45,095 l l pp [571 ABSTRACT [52] U.s. cl. ..335/304, 335/236 A magnet aeaemby fcr ae each aa in a magnetic separater [51] lm. cl. nolh 7/02 hWing mcana fcr Previding increased "nea cf nur increased [58] Field Search ..335/304, 236, 237; 209/219, effective Pce area decreased gaP lengen imPrWed rePeUing 209/223. 21o/222 223 of ux leak lines at the edges of the magnet poles and reduction in the flux leakage at the rear face of the magnet. Herein these means comprise a magnet element disposed at the ex- [56] References Cited tremities of the respective poles to dene aiding poles in the UNITED STATES PATENTS magnetic circuit' 3,069,602 l2/1962 Stout et al ..`....335/236 8 Claims, 7 Drawing Figures MAGNETIC SEPARATOR BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to magnet assemblies and in particular to magnet assemblies for use in magnetic separators and the like. l

2. Description ofthe Prior Art In one improved form of magnetic separator as shown in Buus et al. U.S. Pat. No. 2,992,736 owned by the assignee hereof, a plurality of permanent magnets are mounted in a cylindrical shell with magnet pole pieces disposed between the magnets to provide a flux extending outwardly through the shell for magnetically attracting magnetic solids and the like, such as in slurries, to the cylindrical drum surface thereby to separate such solids from the slurry for suitable delivery to a discharge means. The magnetic separator of said Buus et al. patent provides high efficiency in the separating operation with effectively minimized permanent magnet material in the assembly.

SUMMARY OF THE INVENTION The present invention comprehends an improved magnet assembly such as for use in such a magnetic separator which provides further improved efficiency in the utilization of the magnetic material and improved separating functioning of the magnetic separator.

More specifically, the invention comprehends providing magnetic elements at the outer extremities of the pole pieces to define aiding poles. The aiding poles provide improved magnetomotive force resulting in increased lines of flux useful in the magnetic separating operation. The aiding poles effectively increase the pole area and reduce the gap between the poles to provide improved effective separation. The aiding poles further repel ineffective leak lines at the front edges of the poles. Further, by increasing the desired flux at the front of the magnet assembly a reduction in the undesirable leakage flux at the back of the assembly is obtained.

The utilization of the disclosed aiding poles permits the use of an increased amount of magnet material in the assembly while preventing an increase in the gap between the poles.

BRIEF DESCRIPTION OF THE DRAWING Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein:

FIG. l is a vertical cross-sectional view illustrating a magnetic separator utilizing a magnet assembly of the prior art;

FIG. 2 is a vertical cross-sectional view illustrating a magnetic separator utilizing a magnet assembly embodying the invention;

FIG. 3 is a diagrammatic illustration of a magnetic separator having a magnet assembly ofthe present invention;

FIG. 4 is a diagrammatic elevation of another form of magnetic separator with which the magnet assembly of the present invention may be utilized;

FIG. 5 is a diametric section of another form of magnetic separator provided with a magnet assembly embodying the invention;

FIG. 6 is a transverse cross-section taken substantially along the line 6 6 ofFIG. 5; and

FIG. 7 is a schematic elevation illustrating the utilization of the magnetic separator of the type shown in FIGS. 5 and 6 hereof in separating magnetizable and 'non-magnetizable materials.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the exemplary embodiment of the invention as disclosed in FIGS. 2-5 of the drawing, a drurn type magnetic separator generally designated 10 is shown to include a drum 11 having a magnet assembly generally designated 12 mounted on an axial shaft 13. The magnet assembly is disposed within a cylindrical outer shell 14 and serves to provide magnetic flux outwardly of the shell attracting magnetizable solids from a slurry to the surface of the drum for effectively separating the magnetic solids from non-magnetic solids of the slurry. The drum may be rotated by suitable electric motor drive l5. The magnetic separator may be mounted on a suitable frame 16. The drum 11 may be similarly utilized for separating magnetic solids from a dry mixture, as shown in FIG. 4 wherein the dry material is fed to the magnetic separator by means of a hopper 17. The drum may be similarly rotated by an electric drive generally designated 18.

The magnet assemblies of the prior art utilize stacked permanent magnets such as magnets 19, as shown in FIG. 1. Suitable soft iron ori pole pieces 20 are provided intermediate the end-to-end arranged magnets. For a complete description of such a magnet assembly, reference may be had to the above identified Buus et al. U.S. Pat, No. 2,992,736. As discussed above, the Buus et al. magnetic separator provides an excellent highly efficient separator device. The present invention, however, comprehends a further improved modification of such a magnetic separator providing increased eiciency in the use of the magnetic material by an improved circuit configuration producing increased flux strength and thereby improved separation functioning. Illustratively, the present invention comprehends an arrangement wherein an increase in the flux strength of approximately 20 percent over that of said Buus et al. patent structure is realized.

More specifically, as shown in FIG. 2, magnet assembly 12 includes a plurality of stacked magnets, such as magnets 19a, l9b, 19t` and 19d. The magnets are arranged in magnetic opposition as indicated by the arrows 21 whereby the confronting ends of magnets 19a and 19b comprise the south pole ends of these magnets, the confronting ends of 19b and 19C comprise north pole ends of these magnets, and the confronting ends of [9c` and 19d comprise south pole ends of these magnets. The magnets are secured in the assembly by means of holding plates 22a, 22b, 22C and 22d of non-magnetic material extending between a pair of end plates 23. Triangular shaped pole pieces 24a, 24b and 24C are disposed between the respective confronting magnet ends and end pole pieces 25a and 25b are provided at the opposite ends of the magnet assembly. The magnets may be formed of suitable non-metallic material, such as iron oxide, and at least one metal of the group consisting of strontium, barium and lead. Illustratively, the magnets may be formed of barium or strontium ferrite material of wellknown composition. The pole pieces may be formed of mild steel and the like.

To provide the improved flux strength, aiding poles 26, 27, 28, 29 and 30 are provided in outer recessed corners of the magnets. The aiding poles may be formed of magnetic material similar to the magnetic material of magnets 19a 19d and extend across the outer portion of the gaps between the confronting ends as well as outwardly from the magnet assembly ends adjacent pole pieces 25a and 25b. Each of' the aiding poles inwardly abuts the adjacent pole piece to provide a continuation of the magnetic circuit therefrom to the radially extending outer surface of the assembly. Thus, aiding poles 26, 28 and 30 have their north ends disposed radially outwardly and aiding poles 27 and 29 have their south ends disposed radially outwardly.

The aiding poles increase the magnetomotive force produced in each magnet unit and thus develop an increase in the lines of flux L generated radially outwardly from the assembly for use in the magnetic separation operation. By extending the aiding poles circumferentially beyond the spaces between the pole ends as occupied by the pole pieces, an increase in the effective pole area is provided reducing the effective gap between the poles so as to provide improved magnetic separation. The aiding poles further repel leakage flux at the pole edges such as pole edge 3l. Still further, in such magnetic assemblies some flux is lost at the radially inner portion ofthe assembly illustrated by flux line 32 in FIG. 2. The use of the aiding poles herein effectively minimizes the eect of such leakage at the back of the assembly by virtue of an attraction force produced on the leakage flux. Further, in effect, the aiding poles reduce the reluctance at the outer surface of the assembly as compared to the back or inner surface so as to provide an improved tlux concentration at the radially outer surface.

In illustrating the invention the improved aiding pole structure has been shown as used in conjunction with a magnetic separator assembly somewhat similar to that of the Buus et al. U.S. Pat. No. 2,992,736. As will be obvious to those skilled in the art, the inventive concept is applicable to other pole arrangements and magnet assembly designs. In the illustrated embodiment, the magnet assembly is stationary while the drum is rotatable. As will be obvious to those skilled in the art, the invention is applicable to such magnet assemblies where the magnet rotates as well as with the stationary arrangement. Further, the invention has been illustrated in connection with a magnet assembly utilizing five poles. It will be obvious to those skilled in this art that any number of poles may be utilized in the assembly in conjunction with the aiding pole structure discussed above.

Further illustratively, the aiding pole structure concept may l be utilized with Aa radial pole pulley structure such as structure 32 of FIG. 5. Such a structure is generally shown in Buus et al. U.S. Pat. No. 2,992,733 owned by the assignee hereof` and to which patent reference may be had as to a detailed disclosure of the pulley assembly. Thus, as shown in FIG. 7, the pulley assembly comprises a cylindrical magnetic structure over which a belt 33 carrying material to be separated is passed` As the belt moves about the magnetic separator, the magnetizable material 34 is retained on the belt to a position adjacent the bottom 'of the pulley whereas the non-magnetizable material 35 falls from the belt at the outermost portion of the turn thereof about the pulley. Thus, the two different types of material may be collected in suitable subjacent hoppers 36 and 37.

Briefly, as shown in FIG. 5, pulley 32 includes a shaft 38 coaxially carrying a tubular support 39 mounting a plurality of annular magnets 40 and 41 which may comprise magnets stacked parallel to the axis of shaft 38. Intermediate magnets 40 and 4l is a dual pole piece 42. At the outer end of magnet 40 is provided a pole piece 43 and at the outer end of magnet 4l is provided a pole piece 44, the pole pieces 43 and 44 being mounted to the shaft 38 by means of end hubs 45. The magnet assembly may be enclosed in a non-magnetic tubular cover 46.

The present invention comprehends providing aiding poles at the outer corners of the magnets 40 and 41 to provide similarly improved functioning as provided with magnet assembly 12. Thus, as seen in FIG. 5, an aiding pole 47 may be provided at the confronting ends of magnets 40 and 41 radially overlying pole pieces 42. Aiding pole 48 may be provided at the outer end of magnet 40 overlying pole piece 43 and an aiding pole 49 may be provided at the outer end of magnet 41 overlying pole 44. The aiding poles herein may comprise annular poles having suitable orientation to continue the path of flux F generated to outwardly of cover 46 for effecting the desired magnetic separation functioning. Thus, where the confronting ends of magnets 40 and 4l comprise south poles, aiding pole 47 is arranged to have its radial outer end define the south pole thereof. Aiding poles 48 and 49 are reversely arranged to complete the flux path.

Thus, magnet assembly 32 functions similarly to magnet assembly l2 in providing an improved magnetic separator functioning by means of an improved flux generation and distribution. Each of the features discussed above relative to the aidsembly 32.

Magnet assemblies 12 and 32 are overall dimensionally similar to the magnetic assemblies of the Buus et al. patents disclosed above. Thus, the magnetic assemblies may be substituted in the magnetic separators disclosed therein for improved magnetic separation functioning in the apparatuses of these patents. I'hus the arrangementof the magnet assemblies l2 and 32 avoids obsolescence of existing magnetic separator structure while providing for substantially improved performance thereof by direct substitution in such existing structures.

The foregoing disclosure of specific embodiments is illustrative of the broad inventive concepts comprehended by the invention.

[claim:

l. A magnet assembly comprising: a permanent magnet having spaced north and south poles; a first pole piece at the north pole of the magnet; a second pole piece at the south pole of the magnet, said magnet producing magnetic flux lines about the magnet between said pole pieces; and aiding magnetic pole means of fixed polarity secured to said permanent magnet and extending from one of said pole pieces toward the other of said pole pieces and overlying the one piece for decreasing the effective gap length between said pole pieces and increasing said magnetic flux lines.

2. A magnet assembly comprising: a permanent magnet having spaced north and south poles; a first pole piece at the north pole of the magnet; a second pole piece at the south pole of the magnet, said magnet producing magnetic flux lines about the magnet between said pole pieces; a first aiding magnetic pole means extending from one of said pole pieces toward the other of said pole pieces and overlying the one pole piece for decreasing the effective gap length between said pole pieces; and a second aiding magnetic pole means extending from said other of said pole pieces toward said one of said pole pieces for further decreasing the effective gap length between said pole pieces.

3. The magnet assembly of claim 1 wherein said magnet is provided with a recessed comer adjacent said one of said pole pieces and said aiding magnetic pole means is at least partially disposed in said recessed corner.

4. The magnet assembly of claim 1 wherein said permanent magnet has an inner surface and an outer working surface located between said rst and second poles and said aiding magnetic pole means extends at least partially in a direction away from the inner surface outwardly from the working surface ofthe permanent magnet.

5. The magnet assembly of claim l wherein said aiding magnetic pole means extends at least partially beyond said one of said poles in a direction from said other of said poles toward said one of said poles.

6. The magnet assembly of claim l wherein said aiding magnetic pole means extends away from said one of said poles at least the thickness of said pole piece thereat to fully overlie the face of said one pole piece.

7. The magnet assembly of claim l wherein said magnet comprises an annular series of magnet elements and said aiding magnetic pole means comprises an annular series of magnet elements disposed coaxially of said magnet series.

8. The magnet assembly of claim l further including a second permanent magnet having spaced north and south poles; means mounting said second magnet with one of said poles spaced adjacent the corresponding one of said poles of said first named magnet, one of said pole pieces extending between said adjacent poles, said aiding magnetic pole means further extending from said one of said pole pieces toward the other pole of said second permanent magnet. 

1. A magnet assembly comprising: a permanent magnet having spaced north and south poles; a first pole piece at the north pole of the magnet; a second pole piece at the south pole of the magnet, said magnet producing magnetic flux lines about the magnet between said pole pieces; and aiding magnetic pole means of fixed polarity secured to said permanent magnet and extending from one of said pole pieces toward the other of said pole pieces and overlying the one piece for decreasing the effective gap length between said pole pieces and increasing said magnetic flux lines.
 2. A magnet assembly comprising: a permanent magnet having spaced north and south poles; a first pole piece at the north pole of the magnet; a second pole piece at the south pole of the magnet, said magnet producing magnetic flux lines about the magnet between said pole pieces; a first aiding magnetic pole means extending from one of said pole pieces toward the other of said pole pieces and overlying the one pole piece for decreasing the effective gap length between said pole pieces; and a second aiding magnetic pole means extending from said other of said pole pieces toward said one of said pole pieces for further decreasing the effective gap length between said pole pieces.
 3. The magnet assembly of claim 1 wherein said magnet is provided with a recessed corner adjacent said one of said pole pieces and said aiding magnetic pole means is at least partially disposed in said recessed corner.
 4. The magnet assembly of claim 1 wherein said permanent magnet has an inner surface and an outer working surface located between said first and second poles and said aiding magnetic pole means extends at least partially in a direction away from the inner surface outwardly from the working surface of the permanent magnet.
 5. The magnet assembly of claim 1 wherein said aiding magnetic pole means extends at least partially beyond said one of said poles in a direction from said other of said poles toward said one of said poles.
 6. The magnet assembly of claim 1 wherein said aiding magnetic pole means extends away from said one of said poles at least the thickness of said pole piece thereat to fully overlie the face of said one pole piece.
 7. The magnet assembly of claim 1 wherein said magnet comprises an annular series of magnet elements and said aiding magnetic pole means comprises an annular series of magnet elements disposed coaxially of said magnet series.
 8. The magnet assembly of claim 1 further including a second permanent magnet having spaced north and south poles; means mounting said second magnet with one of said poles spaced adjacent the corresponding one of said poles of said first named magnet, one of said pole pieces extending between said adjacent poles, said aiding magnetic pole means further extending from said one of said pole pieces toward the other pole of said second permanent magnet. 